Haywood began her acting career in 1715 at the Smock Alley Theatre in Dublin. Public records for this year list her as "Mrs. Haywood," appearing in Thomas Shadwell's Shakespeare adaptation, Timon of Athens; or, The Man-Hater.
By 1717, she had moved to Lincoln's Inn Fields, where she worked for John Rich. Rich had her rewrite a play called The Fair Captive. The play only ran for three nights (to the author's benefit), but Rich added a fourth night as a benefit for the second author, Haywood. In 1723, her first play, A Wife to be Lett, was staged.
In the later 1720s, Haywood continued acting, moving over to the Haymarket Theatre to join Henry Fielding in the opposition plays of the 1730s. In 1729, she wrote the tragedy Frederick, Duke of Brunswick-Lunenburgh to honour Frederick, Prince of Wales. George II's son was later a locus for Patriot Whig and Tory opposition to the ministry of Robert Walpole. As he made it clear that he did not favour his father's policies or ministry, praise for him was a demurral. However, when Haywood wrote the play, it is likely that she was still aiming to secure the patronage of the whole royal family, including Queen Caroline, as the royal split had yet to occur.[8] Others, such as James Thomson and Henry Brooke, were also writing such "patriotic" plays (i. e. supportive of the Patriot Whigs) at the time, and Henry Carey would soon satirise the failed promise of George II.
Haywood's greatest Haymarket success came in 1733, with The Opera of Operas, an adaptation of Fielding's Tragedy of Tragedies with music by J. F. Lampe and Thomas Arne). However, it was an adaptation with a sharp difference. Caroline of Ansbach had affected a reconciliation between George I and George II, which meant an endorsement by George II of the Whig ministry. Haywood's adaptation contains a reconciliation scene, replete with symbols from Caroline's own grotto. This enunciated a change in Haywood herself, away from any Tory or anti-Walpolean causes she had supported previously. It did not go unnoticed by her contemporaries.
In 1735, Haywood wrote a Companion to the Theatre. The volume contains plot summaries of contemporary plays, literary criticism, and dramaturgical observations. In 1747 she added a second volume.
After the Licensing Act of 1737, the playhouse was shut against adventurous new plays such as hers.
